Kinetic modeling of direct aqueous mineral carbonation using carbide slag in a stirred tank reactor

•Direct aqueous mineral carbonation by carbide slag was investigated.•A kinetic model based on the two-film theory was developed.•The effect of operating parameters on carbonation and mass transfer was assessed.•An empirical equation between kLa and operating parameters was obtained. Direct aqueous mineral carbonation by carbide slag at various temperatures, power inputs, superficial gas velocities, and CO2 partial pressures in a stirred tank reactor were systematically studied. Based on the Two-Film Theory, a novel kinetic model that exhibited extraordinary agreement with the experimental data was proposed to express the relationship between carbonation efficiency and reaction time. Carbonation efficiencies of more than 90% were achieved in all the experiments. The rate-controlling step of the reaction was gas-liquid mass transfer initially, although solid-liquid mass transfer was the rate-controlling step at the final stage. Changes in the mineralogy and morphology of the carbide slag before and after carbonation confirmed the reaction mechanism. The effect of various operating parameters on gas-liquid mass transfer was quantitatively investigated using an empirical equation. The present study contributes to the large-scale, rational utilization of energy, operation optimization of CO2 mineral carbonation in gas-liquid-solid reaction systems.